The goal of the Phase I feasibility study is to document the statistical parameters for an interactive computer program to assess a person's annual risk for exposure to the AIDS virus (Human Immunodeficiency Virus) based on a sexual history; the program will also simulate the results of behavior changes such as reducing the number of partners, using condoms, and avoiding particular high- risk groups or practices. While seroprevalence rates among different population groups and viral transmission rates for various sexual practices will not be known with any certainty for several more years, an upper bound for each parameter can be estimated from currently-available published studies. The software will be programmed with full user documentation during Phase II, so that the parameters can be changed by the end-user as more information becomes available. The program can be a useful adjunct to counseling in medical settings, worksite wellness clinics, and public health settings, especially STD clinics. A primary goal is reassurance to the "worried well" heterosexual majority that their risk of exposure is, at worst, extremely small and, at best, negligible.